Sharing common ground between lead acid /lithium

Hi Explorers,

I hope someone can give me some advice, I’ve seen a similar question posted but my situation is slightly different.

Wiring my Tinny and want to be able to keep existing crank battery to start motor and operate accessories, outboard will also charge this battery.

I want to add a battery selection switch to allow me to turn battery off, and to allow addition of my camping style lithium battery for longer trips.

Even when the lithium is switched on I will keep the motor connected to the cranking battery, only the accessories will be switched over to the lithium.

The motor is not rated to be started from a lithium battery, older model.

Lithium battery is big enough that I do not need it to be charged by the small motor alternator.

My question is: can I set my wiring so that both batteries share a negative connection - a shared ground.

This would mean that I connect positive for the lithium to one of the switch inputs, the negative from the Anderson plug connection to negative busbar which would also connect to lead acid battery along with all other accessories and motor.

I hope my question is clear and appreciate any assistance you can give.

J